Apparatus for cleaning coal or other granular material



NOV. 11, 1958 s-r 2,859,872

APPARATUS FOR CLEANING COAL OR OTHER GRANULAR MATERIAL Filed Aug. 27. 1954 4 Sheets-Sheet 1 IAIVEA/TOR A2 THUE A. 1112.57

A. A. HlRST 2,859,872

APPARATUS FOR CLEANING COAL OR OTHER GRANULAR MATERIAL 4 Sheets-Sheet 2 Nov. 11, 1958 Filed Aug. 27, 1954 1 Y \AJ AT-- 4 Nov..11, 1958 AT HIRST 2,859,372

APPARATUS FOR CLEANING COAL OR OTHER GRANULAR MATERIAL Filed Aug. 27. 1954 4 Sheets-Sheet :5

A. A. HIRST Nov. 1 1, 1958 APPARATUS FOR CLEANING COAL OR OTHER GRANULAR MATERIAL 4 Shee ts-Sheet 4 Filed Aug. 27, 1954 I l/we/vrae JET/{U2 4 Mesr 9w- IWW' flT-r m Eys Unite APPARATUS FQR CLEANING COAL OR OTHER GRANULAR MATERIAL Application August 27, 1954, Serial No. 452,487

Claims priority, application Great Britain September 1, 1953 11 Claims. (Cl. 209158) This invention relates to an improved apparatus for the cleaning or separation of coal or other granular material. The invention is envisaged as being of particular application to and is described herein with reference to the cleaning of coal, but it is to be understood that the invention may be applied to the separation of granular material other than coal and its associated impurities or dirt and that, when so applied, the less dense granular material will be separated in a manner similar to the coal particles, and the more dense material in similar manner to the dirt particles.

4 One object of the invention is to enable the fine coal in a coal washery slurry to be separated from the fine dirt also present in the slurry; another object of the invention is to enable crude unsized coal to be cleaned with an efliciency approximating to that obtained in the so-called Chance separator using a sand flotation process in which coal is separated from refuse in a heavy medium of sand suspended in water. A further object is to improve the operation of washers for sized coal of the classifier type and known as the Menzies cone separator which consists of a separating cone with a short cylindrical top section provided with a rotating stirrer and with rings of nozzles for admitting water at a number of levels, through nozzles projecting through the sides of the cone. The Menzies cone separator is described in the book entitled Coal Preparation, pages 320-345 published in 1943 in New York, by the American Institute of Mining Engineers.

According to the invention, apparatus for cleaning coal comprises a separating vessel with a conduit for admitting liquid at the bottom of the separating vessel, an'overflow for liquid and solids and a further conduit for admitting liquid at an intermediate level between the bottom of the separating vessel and the overflow, means for feeding coal with or without liquid into the separating vessel at a level higher than the said intermediate level and means whereby, when the pressure head of the liquid admitted to the bottom of the separating vessel exceeds a predetermined value, some or all of this liquid is diverted and admitted to the separating vessel at the said intermediate level.

The supply of part or the whole of the liquid to the vessel may be under a steady or a pulsating pressure and when treating fine coal, this is preferably led in the form of a slurry into the system at a region above the said higher level. Conveniently the liquid used is water.

The conduit supplying liquid to the lowermost region of the tapering vessel may be connected to a head box provided with a weir arranged so that liquid overflowing the weir is diverted to the previously mentioned further conduit for delivering further liquid into the vessel at the higher level. Liquid may be separately admitted to such further conduit irrespective of any liquid diverted to said further conduit as a result of overflow from the weir provided with the head box. The height of the weir and/or the height of the head box may be adjust- States Patent 2 able to permit variation in the pressure at whcih liquid is diverted from the supply to the bottom of the separating vessel.

When slurry is fed into the separating vessel, the

clean coal is carried by the liquid to the top and over flows. Fine dirt collects in the lower part of the vessel and forms a quicksand kept in suspension by the liquid delivered to the base. Any increase in the depth of this quicksand, brought about by the separation of fine dirt, causes an increase in the pressure head of the liquid supplied to the base of the vessel with the result that the level of liquid in the head box rises and ultimately overflows the weir.

In operation, the quantity of liquid supplied to the bottom of the separating vessel, except when diverted by overflowing the weir, is suflicient to produce in the conduit connected to the bottom of the separating vessel a liquid velocity suflicient to prevent the sinking'of the fine refuse forming the quicksand. When, however, part or all of the supply of liquid to the base of the separating vessel overflows the weir the velocity in the conduit at the bottom of the separating vessel becomes insuflicient to support the quicksand which, therefore, sinks through the conduit until liquid ceases to overflow the weir. By this means the depth of the quicksand of the fine refuse is automatically kept constant.

The conduit receiving the liquid which overflows the weir and is diverted from the base of the vessel is preferably connected to the said vessel at a level only slightly above the base so that the total quantity of liquid flowing through the quicksand remains constant irrespective of'the operation of the control effected by the weir, and as a result, conditions in the quicksand are maintained substantially uniform at all times.' This leads to two advantages firstly, the effective density of the quicksand remains substantially constant irrespective of the effect of the weir control on the supply of water to the base of the vessel, and secondly, by maintaining at all times a freely moving quicksand, the conduit connected to the base of the vessel does not tend to choke when the operations of the weir control decreases the quantity of liquid fed in through the said conduit.

In an alternative arrangement the head box is connected by two conduits one leading to the base of the vessel and the other to a higher level in the vessel, but liquid is supplied to the vessel independently of either or both conduits. In some cases, this alternative arrangement provides a rather more convenient layout of the separating apparatus and control equipment, but" the method of operation is the same as that described earlier in which, when the pressure head at the base of the vessel exceeds a predetermined limit, liquid overflows the weir in the head box and is diverted from the base of the vessel to a higher level.

A pulsating eifect may be provided in the liquid in the vessel to improve separation. This may'be obtained by any suitable means, e. g., a pulsating air supply as in the case of a pneumatically operated washer box.

By way of example various embodiments of the invention are hereinunder described with reference to the accompanying drawings.

In the drawings;

Figure 1 is a diagrammatic representation of one form of the invention;

Figure 1A is a section on the line AA of Figure 1;

Figure 2 is an enlarged view of the chamber system;

Figure 3 is a diagrammatic representation of an alternative form;

Figure 4 is a diagrammatic representation of a still further alternative form.

Figure is a diagrammatic representation of a still further form.

Referring to Figures 1 and 2, a separating vessel comprising a lower conical chamber 1 tapering towards its base and an upper conical chamber 11A is provided with a feed pipe, for coal slurry, 2A having an inlet connection 2B to a further conical chamber 2 arranged below the conical chamber 1A. An inlet connection 413 sup plies liquid from a pipe 4A to the bottom of the conical chamber 1 via the chamber 4 and conduit 7C. A further-inlet connection 313 supplies liquid from a pipe 3A to an intermediate level in the separating vessel, close to the bottom of said vessel, via the chamber 3. The liquid suppliedto the connections 4B and 33 may conveniently be water.

The liquid supply at 3A is connected via pipe 3F to a head box 3C and the-liquid supply at 4A is connected via pipe 4F to a head box 4C, the liquid level in those twoboxes beinginterconnected by an automatic weir 5 whereby .when the level of the liquids in box 4C exceeds agiven value the liquid overflows to box 3C.

The liquid supply at 3A is also connected via pipe 31) to a pulsating air supply 315 and the supply at 4A is similarly connected via pipe 4D to a pulsating air supply 4E. A third pulsating air supply 613 is led via pipe 6D into a tube 6 closed at the top and open at the bottom which is submerged in liquid.

The chamber 1 has an outlet 7 for the discharge of fine dirt, this exit being provided with valves 7A, 7B, only oneof which is open at a time for discharge of the dirt. A water seal 8 is also provided at the end of the outlet 7.

Referring to Figure 2, the conical chamber 1 is providedat its lower end with a spigot 7C through which liquid supplied to part 4 from inlet 4B is admitted to the: conical chamber 1.- The spigot 7C may be a removable interchangeable element to enable spigots of other dimensions to be inserted to suit operating conditions. The upper part of the system is provided with a central tube 6 which is preferably arranged to be capable of vertical movement and which is open at its lower end. In this arrangement the liquid enters at 3B and 4B, passes upwards through the part 4 and chamber 1 and around the tube 6 and finally overflows at the top of the system, the fine coal emerging at the four exits 13. The fine dirt forms a quicksand in the teeter zone 10, the dirt being discharged through the spigot 7C and the discharge tube 7.

The inlet connection 2B for the coal slurry admitted through the pipe 2A is arranged tangentially to the separating cone 1A so that, prior to entering the said cone, the feed is caused to travel spirally in a downwards direction in the annular space between the lower part of the cone 1A and the walls of the part 2. The effect is to provide a uniform distribution of the feed of slurry in the lowermost zone of the cone 1A and to cause rotation of the slurry within the system. The inlets 3B and 4B for the pipes 3A, 4A respectively arranged in similar fashion as shown in Figure 2. The rotary movement thus imparted to the slurry tends to promote uniform separating conditions within the apparatus.

Coal, separating to the top of the separating vessel overflows together with liquid through the four overfiow connections 13. Refuse settles towards the bottom ofthe vessel. The largest and heaviest particles of dirt may sink through the current of liquid admitted through the spigot 7C, but some, at least, of the fine dirt, will be prevented from so doing by the velocity of the flow through the spigot 7C.

For satisfactory operation it is desirable that the level of the quicksand should be approximately constant and that the fine dirt should not choke up the spigot 7C. Automatic control of the quicksand level is effected by means of the head boxes 3C, 4C. If the level of the quicksand rises, this increases the pressure head in head 4. box 4C. The level of the liquidin this head box therefore rises, overflows the weir 5, and enters the head box 3C, with the result that the quicksand sinks through the spigot 7C whereby the pressure in headbox 4C falls so that the level of the quicksand is caused to fall once more to its original level. By arranging either for the vertical height of the Weir 5 or for the vertical height of the boxes 3C and 4C to be adjustable, the level of the quicksand can be maintained at any desired value.

A ball 15 suspended from a chain 15A can be lowered when desired to the position shown in dotted lines so as to close the upper end of spigot 7C.

In the case of failure of the supply of liquid to pipes 3A and 4A, the ball is lowered to prevent the contents of the separating vessel'from sinking through the spigot 7C, thereby tending to choke the apparatus for discharging refuse from the chamber 7.

Figure 3 shows a possible modification of the arrange.- ment in which the conical chamber ll together with liquid supplies at 3A and 4A are the same as that described above Pulsations are produced in two vessels 11 which produce an effect equvialent of a diaphragm pump and these vessels are connected through two pipes 11A to one-way valves 11B, 11C in the discharge pipe 7. One vessel 11 operates one pair of valves 11B, 11C all of which open only in the downward direction. The efiect of the pulsations in the vessels 11 is to cause the fine dirt together with a regulated quantity of liquid to pass from the pipe 7 into a vessel 17 and a pipe 12 from the top end of which the refuse is finally discharged.

To assist in the discharge of fine dirt a fresh water pipe 18 is connected to the vessel 17.

In the arrangement described in Figure 3 it is necessary for correct operation to admit through the pipe 4A sufiicient liquid to provide the required flow through the spigot 7C plus a quantity equivalent to that discharged with the fine refuse through the one-way valves 11B and 11C.

A pulsating air supply is also connected to the interior of the central tube through a pipe 6D and valve 6E. If the separating vessel is used further to clean the coal slurry produced by a-Baum washer'box the valve 6E may be connected to one of the air chambers of the said Washer box.

The invention may be applied to known coal washers of the classifier type using a conical cleaning chamber. As one example of such application the invention may be applied to the Menzies cone separator of the kind wherein liquid is fed to the cone at its base and at a number of higher levels andmeans are provided whereby when the pressure of the liquid delivered through the base is above a given value, part or all 'of the liquid is by-passed or is led to-the surface of the liquid in the cone, a central rotatable shaft carrying stirring arms for stirring the liquid. In applying the invention to this kind of classifier the by-passed liquid is led to an intermediate level in the cone instead of to the surface of the liquid in the cone or to waste as in known practice. By returning the bypassed liquid to such intermediate level a constant flow through the conical separating chamber is maintained.

Figure 4 illustrates this application of the invention and shows the modifications required to the type of classifier known as the Menzies Cone Separator. The head boxes 3C and 4C and the weir 5 correspond with the similarly numbered parts in Figures 1 and 3. In the normal Menzies separator any liquid overflowing the adjustable weir 5 is returned either directly to the sump of the pump 33 or indirectly theretovia the surface water of the cone 34. In the present invention water overflowing the adjustable weir 5 from the head box 4Cisreturned to a low level in the cone via the head box 3C and the pipe 3A. In Figure 4 the pipe 3A is connected to one of the pipes 30' connected to a ring of nozzles 31 supplying water under pressure to the lowest level in the cone, but the pipe 3A could be connected near the bottom of a to any particular method of refuse removal.

separate inletto the cone. In order to prevent blockage of the pipe 3A, water may be separately supplied to the head box 3C. A stirrer is indicated at 32 and an elevator for removing dirt is shown at 35.

It will also be understood that a stirrer may be incorporated in the apparatus of Figures 1 and 2 and Figure 3.

Another possible application of the invention is to the known apparatus of the kind in which coal is separated from refuse in an artificial heavy medium of sand suspended in water in a conical chamber. In this case the apparatus is modified by the provision of two pipes, one connected to the refuse tube or to the cone immediately above the refuse tube and the other to an intermediate level in the cone, each being connected to head boxes as previously described in connection with Figure 1. Water may be supplied to either or both conduits and, although the modification will operate without such supply of water, it is preferred to admit some water to both conduits in order to prevent the accumulation therein of sand, par- 1 ticularly in that conduit connected to the higher level in the cone. The effect of this modification is that any water which overflows the weir 5 is returned to a level in the cone above the refuse tube thereby improving the separation of fine and near-gravity refuse particles which are caused to settle in the refuse tube instead of being prevented from doing so by the liquid current in the tube or the lower part of the cone. This arrangement also provides some degree of automatic'control of the density of the sand suspension since if the density is too high some of the sand is discharged via the refuse tube.

The modifications required to the normal type of Chance Separator will be similar to those necessary in the case of the Menzies Cone, and involve the addition of parts 3A, 3C, 4A, 4C and 5, connected as in Figure 4. It is to be understood that the invention is not confined If refuse is discharged via a refuse chamber supplied with intermittently operated refuse gates, the'pipe 4A will be connected to the classifier column at the bottom of the conical separating chamber, that is the pipe between the base of the Chance Cone and the upper refuse gate, through which pipe water is admitted to the bottom of the cone.

Still another application of the invention is to provide a still further modification of the last mentioned apparatus as illustrated in Figure 5, this arrangement being intended to be able to clean unscreened coal in ranges of, for example, about 6" to zero. In this arrangement the separation of the coarser sizes of material is similar to that of a Chance Sand Separator, modified according to the present invention, as hereinbefore described with reference to Figure 4, but the heavy medium consists of a suspension of fine refuse instead of sand. A separating cone 25 is provided with stirring mechanism 32 and means for admitting liquid at the base at 19 and at a number of higher levels at 31, as in the case of the Menzies or Chance Cones. The cone is, in general, similar to a Chance Cone, but is provided with head boxes 3C and 4C, pipes 3A and 4A, and adjustable weir 5, connected to the cone as in the manner hereinbefore described and illustrated in Figure 4. Unsized coal is delivered at 24 into the top of the separating cone 25. Dirt-sinks to the bottom of the discharge pipe 19 and is raised by an elevator 20 while the coal and water together with some of the fine dirt including that constituting the suspension medium, overflows the top of the cone and is delivered to a screen 21. The slurry passing through screen 21 is delivered by means of pump 26 to a settling vessel 22 from the base of which a pipe 23 leads to a slurry separator 27, and a proportion of the fine dirt from the slurry separator is returned at 28 by an elevator 29 to the cone in order to provide material for quicksand or dense medium. The remainder of the fine'dirt is discharged at 36 to waste.

It is to be understood that, if the raw coal fed to cone 25 should contain'a sufficiently high proportion of fine refuse, it may be unnecessary to feed in additional quantities of fine dirt at 28 and that in any event the proportion of fine refuse fed to cone 25 from the elevator 29' will be controlled to provide a correct suspension medium.

If desired the finer sizes of refuse may bescreened from the dirt delivered by the elevator 20 and pipe 37 and part or all of this fine refuse may be returned to the cone 25 to provide extra suspension material.

In Figure 5 the slurry passing the screen 21 is treated,

after settlement, by the separating cone 27 which is designed according to the present invention, but it is to be understood that, instead of the cone 27, any other type of separating apparatus, suitable for fine material, could be used. Y

The separating cone 27 is provided with an elevator 29 for removing fine dirt. The fine dirt thereby. ad mitted at 28 to the cone 25 contains a relatively low proportion of liquid. If the method used for removing fine dirt from the cone 27- should be such that this material is removed with a relatively high proportion of liquid, it may be necessary partially to concentrate the mixture of fine solids and liquid, by settlement or other means, prior to delivering the fine refuse particles to cone 25. It is to be understood that extra liquid may be added at 28 with the fine refuse, if the latter is delivered in too concentrated a form by the separating apparatus for the fine material.

In the separating cone 25, the method of removing dirt by means of an elevator is described solely by way of example and it is to be understood that the invention is not confined to this particular method.

I claim:

1. In an apparatus for cleaning granular material such as coal, the combination comprising a separating vessel, a conduit admitting liquid at the bottom of said separating vessel, an overflow for liquid and solids from said separating vessel, a further conduit for admitting to said separating vessel liquid at an intermediate level between the bottom of said separating vessel and said overflow, means for feeding granular material into said separating vessel tangentially at a level higher than the said intermediate level, and diversion means whereby, when the pressure head of the liquid admitted to the bottom of said separating vessel exceeds a predetermined value, at least some of this liquid is diverted and admitted to said separating vessel at the said intermediate level.

2. In an apparatus as claimed in claim 1, the construction wherein said diversion means comprises a headbox connected to said conduit supplying liquid to the bottom of said separating vessel, and in said head-box a weir arranged so that liquid overflowing said weir is diverted to said further conduit for admitting liquid to said separating vessel at the said intermediate level.

3. In an apparatus as claimed in claim 2, the connection of said conduit receiving the liquid overflowing said weir in said head box to said separating vessel at an intermediate level only slightly above the bottom of said separating vessel so that the total flow of liquid through the lowermost zone of said separating vessel remains constant irrespective of the operation of the control effected by said weir.

4. In an apparatus as claimed in claim 1, the pro vision of means for producing a pulsating flow of at least part of the liquid entering said separating vessel.

5. In an apparatus as claimed in claim 1, the provision of a tube connected to a pulsating air supply and open at its lower end and having its lower end submerged in the liquids and solids contained in said separating vessel.

6. In an apparatus as claimed in claim 1, the provision of a valve lock connected to said conduit for supplying liquid to the bottom of the separating vessel for tliremoval" of refuse sinking through the liquid in the said conduit.

7. In an apparatus as claimed in claim 6, the provision of a one-way valve connecting said valve lock to said conduit supplying liquid to the bottom of said separating vessel, a further one-way valve for discharging refuse, and means for producing liquid pulsations.

8. In an apparatus as claimed in claim 1, means whereby further liquid is admitted to said separating es-t sel at least one further level above the said intermediate level;

9. Inan apparatus as claimed in :claim 1, the provision -of a screen, means whereby the granular material and liquid overflowing from said separating vessel is fed to said scre'en,'a second separator, means whereby slurry passing through said screen is fed to said second separator, and means whereby at least part of the refuse product of said second separator isreturned to said separating vessel so as to constitute, together with the liquid in the separating vessel, a dense separating medium.

diverted and admitted to said separating vessel in a man ner such that said liquid enters said separating vessel tangentially at said intermediate level and thereby imparts a rotary movement to the contents of said separating vessel.

References Cited in the file of this patent UNITED STATES PATENTS 1,224,138 Chance May 1, 1917 2,220,925 Walker Nov. 12, 1940 2,733,810 Murry Feb. 7, 1956 

